Vascular stents

ABSTRACT

The disclosure describes a coating for medical implants, in particular, vascular stents, said coating comprising silicon dioxide, towards medical implants with a coating containing silicon dioxide and towards a method for their production. The coating can contain additional admixtures and have functionalization coats. The substrate of the coating is produced from a durable material, preferably from a stainless steel.

BACKGROUND OF THE DISCLOSURE

The disclosure relates generally to the field of medical implants, inparticular, a vascular stent, for example, for implantation in the bloodvessels of a body.

BRIEF SUMMARY OF THE DISCLOSURE

So-called “stents” are deployed in vessels at risk of occlusion, for thepurpose of holding open vessels, such as blood vessels (in the case ofarteriosclerosis). This can either be done by means of a catheter or bymeans of surgically opening the vessel, clearing it out where necessaryand implanting the stent. Stents are generally cylindrical, tubularstructures, for example, woven fabric tubes or pipe-like porousstructures, that nestle against the inner wall of a vessel and hold openan unrestricted cross-section of the flow through which the blood in theblood vessel can flow freely.

Further uses of stents are in bile ducts, airways or the esophagus. Forexample, stents are used in the treatment of carcinomas for the purposeof restricting the stenoses in the respiratory tract, bile ducts oresophagus after dilatation has taken place.

There is a need for medical implants, such as stents, for example, thatallow easy implantation in the body of a patient.

DETAILED DESCRIPTION

Stents are deployed in vessels at risk of occlusion, for the purpose ofholding open vessels, such as blood vessels (in the case ofarteriosclerosis). This can either be done by means of a catheter or bymeans of surgically opening the vessel, clearing it out where necessaryand implanting the stent. Stents are generally cylindrical, tubularstructures, for example, woven fabric tubes or pipe-like porousstructures, that nestle against the inner wall of a vessel and hold openan unrestricted cross-section of the flow through which the blood in theblood vessel can flow freely.

Further uses of stents are in bile ducts, airways or the esophagus. Forexample, stents are used in the treatment of carcinomas for the purposeof restricting the stenoses in the respiratory tract, bile ducts oresophagus after dilatation has taken place.

Stents often consist of tubes with reticular walls that have a smalldiameter, because of which they can easily be brought to the destinationby means of a catheter, where they can be expanded with the help of aballoon (balloon catheter) in the vessel by stretching the reticularwall of the stent to the necessary lumen and therefore the diameternecessary for supporting the vessel.

It is known to coat stents with plastics, such aspolytetrafluoroethylene (PTFE; TEFLON®), for example.

Inherent in known stents, however, is the problem that, because of theirspecific surface and their mesh structure, the body's cells often growthrough or over the stents, which can, in turn, over the long run leadto a renewed occlusion of the vessel that had been secured with a stent.In this case, it is difficult to find the desired compromise betweenholding open the vessel and harmoniously integrating the stent into theorganism. The conventional stent coatings are also not always flexibleenough to go along with the stent's movements during implantation andexpansion, which can result in damages to the coating. It has also beenseen that an electronic potential can build up between the stentmaterials and the blood or other tissue, wherein such potentials canadversely modify the properties of the blood components in the layerbordering the stent materials, as a result of which uncontrolleddeposits, such as plaques, can result. These problems are also found tosome extent in other medical implants with similar requirements.

This need is solved by the provision of herein of coatings, medicalimplants, and methods for the production of a coated medical implants.Further advantageous embodiments, aspects and details of the disclosureunder consideration are evident from the description herein.

An object of the present description is to provide a medical implant,such as a vascular stent, with a coating containing silicon dioxide, or,in other words, a glass-like coating. Accordingly, the disclosure isdirected towards a coating for medical implants, said coating containing(i.e., including) silicon dioxide. The silicon dioxide can be present inan amorphous or crystalline or semi-crystalline form. The medicalimplant is preferably a vascular stent, for example, for blood vessels,bile ducts, esophagi or airways.

The properties of the coating can furthermore be modified by at leastone admixture that is contained in the coating, wherein the admixturecan be selected from aluminum oxide, titanium oxide, calcium compounds,sodium oxide, germanium oxide, magnesium oxide, selenium oxide andhydroxides, in particular, hydroxides of the previously mentionedmetals. Particularly preferred admixtures are aluminum oxide andtitanium oxide. If an admixture to silicon dioxide is used, the ratio ofthe admixture to the total quantity of the coating can preferably be 0.5to 50% by weight.

In order to retain the desired surface properties across the entiresurface of the medical implant, such as a vascular stent, it ispreferred that the coating be essentially pore-free.

With specific embodiments, however, it can likewise be preferred thatthe coating have pores for functionalization with additional substances,which are applied to the coating after the actual coating process andwhich deposit in the pores. Accordingly, the coating described hereincan have an additional functionalization coat, even applied onlypartially or at selective points. Such a coat can correspond to themedical purpose of the medical implant and comprise an influencing ofthe growth of surrounding tissue, a killing off of unwanted tissue,building up a relationship between the medical implant and tissue, etc.The functionalization coat can, for example, contain a medicine, a cellpoison, or both.

A major advantage of the medical implants described herein is to be seenin that the coating can be applied in an extremely thin layer, namely,preferably in the nano-range, meaning in the range of single atomlayers, which permits the final dimensions essentially to be selectedduring the production of the medical implant without it being necessaryto take into account dimensioning changes caused by the coating that maynot be predictable with precision. The thickness of the coatingdescribed herein is preferably 0.1 to 1000 nm, but it is understood thatboth thinner and thicker coatings are possible. Decisive in theselection of the layer thickness is the requirement that the coating notbe damaged during the expansion of the implant in the body and that noadditional pores be formed.

The coating can be applied in a single step, and thereby form a singlelayer, but can, in a preferred embodiment, also consist of multiple,successively applied layers. In the multi-layer method, the compositionof each individual layer can be defined separately.

This disclosure is furthermore directed towards a medical implant thathas a substrate that forms a basic structure and a coating applied to atleast sections of the substrate, wherein this coating contains silicondioxides or is made of silicon dioxides. In particular, the coating is acoating described herein.

The medical implant is preferably a vascular stent. The vascular stentcan be intended for a blood vessel, a bile duct, the esophagus or thetrachea, wherein it can be deployed for various types of animals, suchas humans, pets and production animals.

The substrate is preferably constructed from a difficult-to-degradematerial, whereby “difficult-to-degrade” is taken to mean a property inwhich the material shows no visible signs of degrading for at least oneyear after implantation in a body.

For medical implants, particularly vascular stents, the substrate cancomprise customary materials, such as carbon, PTFE, DACRON®, metalalloys or PHA, wherein steel alloys in particular are preferredmaterials. The metal alloys that can be deployed for the substrate arepreferably selected from stainless steels. A further preferred materialfor the substrate is a shape memory metal, in particular, nickeltitanium alloys, which are used for stents because of their facultiesfor independent shape modification.

This disclosure is likewise directed towards a method for the productionof a medical implant, in particular of a medical implant describedherein, the method having the steps of provision of a substrate formingthe basic structure and application of a coating containing silicondioxide by means of a plasma coating method. All that has been disclosedwith regard to the coating or the medical implant also appliesanalogously to the methods described herein and vice versa, so thatthese are referred to alternately.

In order to obtain the desired pores for holding means offunctionalization in certain embodiments, it is furthermore preferredthat the method comprises the step of producing the pores in the coatingby means of neutron bombardment. For this purpose, neutron sources, suchas particle accelerators, for example, can be used. A further variantfor producing the function pores consists of manufacturing the pores bymeans of laser light.

The subject matter disclosed herein includes a coating for medicalimplants, in particular vascular stents, which, because of its inert,glass-like surface with silicon dioxide, largely prevents the growth ofcells of the body or attachment of such cells, which, because of itshardness, counteracts damage when the implant is introduced into thebody, therefore simplifying the handling, which, because of the thinnessof the coating, permits a simpler design of the implant, has reducedfriction as a result of low roughness levels and therefore a smallerimpact on blood components and lower coagulation formation and in whichthere is no degradation of the coating whatsoever, even after a longerstay in the body.

The disclosure of every patent, patent application, and publicationcited herein is hereby incorporated herein by reference in its entirety.

While this subject matter has been disclosed with reference to specificembodiments, it is apparent that other embodiments and variations can bedevised by others skilled in the art without departing from the truespirit and scope of the subject matter described herein. The appendedclaims include all such embodiments and equivalent variations.

1. A coating for a medical implant, the coating comprising silicondioxide, wherein the thickness of the coating is from 0.1 to 1000nanometers.
 2. The coating of claim 1, wherein the medical implant is avascular stent.
 3. The coating of claim 1, wherein the coating furthercomprises at least one ingredient selected from the group consisting ofaluminum oxide, titanium oxide, calcium compounds, sodium oxide,germanium oxide, magnesium oxide, selenium oxide, aluminum hydroxide,titanium hydroxide, sodium hydroxide, germanium hydroxide, magnesiumhydroxide, selenium hydroxide, and mixtures of these.
 4. The coating ofclaim 3, wherein coating comprises the ingredient in an amount ofapproximately 0.5 to 50% by weight of the coating.
 5. The coating ofclaim 1, wherein the coating is essentially free of pores.
 6. Thecoating of claim 1, wherein the coating includes pores.
 7. The coatingof claim 1, wherein the coating further comprises a functionalizationcoat.
 8. The coating of claim 7, wherein the functionalization coatcomprises at least one of a medicine and a cell poison.
 9. (canceled)10. The coating of claim 1, wherein the coating includes multiplelayers.
 11. A medical implant comprising a substrate having a coatingthat is applied to at least a section of the substrate and thatcomprises silicon dioxide.
 12. The implant of claim 11, being a vascularstent.
 13. A medical implant having at least a section coated with thecoating of claim
 1. 14. The implant of claim 11, wherein the substratecomprises a difficult-to-degrade material.
 15. The implant of claim 11,wherein the substrate comprises a material selected from the groupconsisting of carbon, PTFE, DACRON®, metal alloys and PHA.
 16. Theimplant of claim 15, wherein the substrate further comprises an ironalloy.
 17. The implant of claim 16, wherein the iron alloy is astainless steel.
 18. The implant of claim 14, wherein the substratefurther comprises a shape memory metal.
 19. The implant of claim 18,wherein the shape memory metal comprises a nickel-titanium alloy. 20.The implant of claim 12, wherein the vascular stent is suitable for usein at least one of a blood vessel, a bile duct, an esophagus, and atrachea.
 21. A method for producing a coated medical implant, the methodcomprising: providing a substrate forming the basic structure of theimplant; and applying to the substrate a coating comprising silicondioxide by means of a plasma coating method.
 22. The method of claim 21,further comprising the producing pores in the coating using a methodselected from the group consisting of neutron bombardment andapplication of laser light.